The invention relates to rotary regenerative heat exchangers and, more particularly, to a method of constructing a cylindrical rotor assembly for a rotary regenerative heat exchanger of the type wherein the rotor is mounted about a rotor post that is disposed along a vertical axis.
Conventional rotary regenerative heat exchangers are comprised of a rotor assembly which is surrounded by a housing having end plates formed with openings arranged to direct the flow of a heating gas and a gas to be heated through the housing to transverse the rotor assembly disposed therein. The rotor assembly is formed of a rotor compartment surrounding and mounted to a rotatable central rotor post. The rotor compartment is formed of a plurality of sectors defined by radial partitions, termed diaphragms, mounted to and extending radially outward from the rotor post. Each of these sector compartments carries heat absorbent material in the form of metallic plates which are first positioned in the heating gas stream to absorb heat therefrom and then moved, as the rotor rotates, into the stream of gas to be heated to transfer the absorbed heat thereto.
Typically, such a rotary regenerative heat exchanger is of such a size to preclude it being shipped from the manufactured plant to the erection site as a complete unit. Therefore, it has become customary to manufacture the rotor assembly in subsections which may readily be shipped, typically by truck, rail or barge, to the erection site where the complete heat exchanger is assembled. One method of manufacturing such a rotor assembly in sections for subsequent field erection is disclosed in U.S. Pat. No. 3,267,562 of Chiang et al. As disclosed therein, a plurality of individual sector compartments are prefabricated in the shop and then shipped with the rotor post to the field for erection. The rotor post comprises a cylindrical post having a plurality of circumferentially spaced axially elongated rib plates extending radially therefrom to which the sector compartments are bolted and welded when the heat exchanger is constructed in the field. Each of the prefabricated sector compartments comprises at least a pair of diaphragm plates interconnected by transverse support members. The rib plates extending from the rotor post comprise axially elongated plates of structural steel which are welded to the rotor post along a vertical seam.
An alternate method of constructing a vertical rotary regenerative heat exchanger is disclosed in U.S. Pat. No. 3,891,029 of Mahoney. As disclosed therein, the rotor assembly is again constructed in the field from a plurality of individual prefabricated sector compartments which in this case are each adapted to be secured to the rotor post only by a pin connection at the upper end and the lower end of the rotor post. Each of the individual sector compartments comprises a pair of radially extending diaphragm plates interconnected by transverse structural grid members. The rotor assembly is typically comprised of up to 24 of such prefabricated sector compartments. To erect the heat exchanger in the field, each of the individual sector compartments is pinned to the rotor post at the top and at the bottom of the rotor post and then the diaphragm plates of juxtadisposed sector compartments are bolted together. Thus, at the interface of each of the sector compartments there are double diaphragms. Although such a design has eliminated the welding of the rib plates to the rotor post as a means of supporting the sector compartments, the use of double diaphragms at the interface of each of the sector compartments adds structural weight and cost to the manufacture of the rotor assembly.